Arc tube mounting



1968 K. GOTTSCHALK ARC TUBE MOUNTING Filed Nov. 14, 1966 Fig 1.

lnven tor': Klaus Go t tschalk b9 4' His A t tca neg United States Patent Office 3,409,790 Patented Nov. 5, 1968 3,409,790 ARC TUBE MOUNTING Klaus Gottschalk, Cleveland Heights, Ohio, assiguor to General Electric Company, a corporation of New York Filed Nov. 14, 1966, Ser. No. 594,220 4 Claims. (Cl. 31325) This invention relates to high intensity electric discharge lamps having an arc tube mounted in a vitreous outer envelope or jacket, and more particularly to the mounting arrangement or structure for supporting the arc tube.

A common high intensity lamp is the high pressure mercury vapor lamp which generally comprises a quartz arc tube enclosed within a glass outer jacket fitted with a screw base at one end. Other kinds of high intensity lamps use different gas or vapor fillings within the arc tube; for instance the mercury metal halide lamp has a filling of mercury plus various metal halides, primarily sodium iodide. Some are tubes are of material other than quartz; for instance a known high pressure sodium vapor arc tube utilizes an alumina ceramic envelope. The outer envelope or jacket may be left clear or may be coated internally with a phosphor in order to improve the quality or the total quantity of light emitted by the lamp.

The principal object of the invention is to provide a new and improved mounting or support structure for the arc tube in a jacketed lamp which is easy and economical to manufacture and which will reliably withstand the stress and abuse of handling and use.

In a jacketed lamp embodying the invention wherein the outer envelope is provided with a re-entrant dimple at its closed or domed end, the arc tube supporting frame engages the dimple by means of a springy clip which makes slightly less than a full loop around it. The supporting frame may be a wire harness which extends from the stem at the base end of the outer envelope to the dimple at the closed end. According to the invention, part of the harness forms a half loop around the dimple and the springy clip is attached to the harness in such fashion that the gap in the clip faces into the half loop. The springy clip provides a resilient engagement accommodating a wide range of dimensional variations in the outer envelopes, and the arrangement assures that in case of a blow to the lamp sufficient to force the dimple out of the spring clip, the half loop of the wire harness limits the movement and retains the dimple and the clip interengaged.

Further advantages and features of the invention will appear from the following description and accompanying drawing illustrating a preferred embodiment, and the features believed to be novel will be more particularly pointed out in the appended claims.

In the drawing:

FIG. 1 is a side view, partly in section, of a high pressure mercury vapor lamp with the improved arc tube mounting of the invention.

FIG. 2 is an end sectional view looking upon line 22 in FIG. 1 and showing the engagement of the dim ple in the domed end of the outer envelope.

Referring to the drawing, there is shown a high pressure mercury vapor lamp 1 comprising an outer vitreous envelope or jacket 2 of ellipsoidal shape. The neck 3 of the outer envelope is closed by a re-entrant stem 4 having a press 5 through which extend relatively stiff inlead wires 6, 7 connected to the contacts of the usual screw type base 8, namely the threaded shell 9 and the insulated center contact 11. At the domed end of the envelope, there is provided a recess or dimple 12 of generally cylindrical configuration with side walls tapering in slightly.

The quartz inner arc tube 14 encloses a charge of mercury and an inert star-ting gas and is provided with a pair of main electrodes 15, 16 on inleads hermetically sealed through the pinched ends 17 of the arc tube by conventional ribbon seals 18. An auxiliary starting electrode 19 at the base end of the arc tube is electrically connected to main electrode 15 at the opposite end through a current limiting resistor 20.

In the illustrated lamp corresponding to a 400-watt size, the frame which supports the are tube within the outer envelope comprises a single vertical portion or side I rod 21 extending axially from the stem at the base end The illustrated single side rod harness causes minimum obstruction of light. In larger sizes of lamps, for instance 1,000 watt lamps, where more support is needed, a similar frame may be used but having two side rods, the second rod being realized by extending side portions 22,

u 24 to meet together.

The .frame is anchored at its upper end to dimple 12 by means of a springy clip 28 which makes slightly less than a full loop around the dimple. A gap in the clip is desirable because it facilitates forcing the clip onto the dimple during assembly of the lamp. Wire portion 25 of the harness is shaped to make a relatively wide half-loop 29 around the dimple, that is, wide enough normally to avoid contact and be clear of the dimple, and the clip is welded to it and oriented so that the gap faces into the interior or concave side of the half loop. As illustrated, springy clip 28 consists of straight-sided segments tending to form a hexagon. Five of the segments are complete and the gap in the loop occurs between the vestigial segments 30, 31. The wire half-loop 29 is shaped in complementary fashion to form half a hexagon. One of the intermediate segments of the clip is welded to the wire harness at 25a (FIG. 2) and the clip is so positioned that the gap between the vestigial segments 30, 31 faces into the half-loop. The resiliency in the attachment comes from the springy clip 28 which should be made of a material which will withstand the heat of welding to the harness portion without losing its temper; a suitable material is Monel metal consisting of an alloy of nickel and copper, but stainless steel may also be used.

In fabricating the lamp, the mount assembly comprising the wire harness fastened to the stem and having the are tube clamped into it is inserted into the outer envelope by sliding it through the neck and forcing springy clip 28 onto dimple 12. In order to avoid bending or distorting the wire frame when the clip is driven home around the dimple, a clip which is relatively light at the same time as it is springy must be used. Finally in sealing the stem 4 to the neck, it is desirable to work the glass of the juncture by pulling and pushing the stem and mount assembly relative to the envelope 2 in order to stretch and compress the soft glass at the joint; the grip of springy clip 28 on the dimple must be light enough to allow the necessary sliding movement. The foregoing requirements for lightness in the springy clip present the danger that should a lamp be dropped or subjected to a sharp blow after assembly, the clip may be forced open and the dimple become disengaged with the result that the arc tube would be permanently cocked over to one side of the outer envelope. The invention forestalls such possibility by facing the gap in the clip into the interior of half-loop 29; with this arrangement,

gaging either clip or the dimple directly before complete disengagement can occur.

. In copending application Ser. No. 400,016, filed 'Sept. 29, 1964 of Everett Niles, entitled Arc Tube Mounting now Patent No. 3,294,998 and assigned to the same assignee as this invention ,the attachment of the wire harness to the dimple is achieved by forming part of the harness into a half-loop around the dimple and using a springy clip attached thereto to complete the loop. In comparing the present construction with that of the Niles patent, the present construction was found to allow a greater range of variations in bulb molding and dimple dimensions while giving higher resistance to pull-out in all directions, that is resstance tohand-spreading of the clip to accommodate an oversized dimple, or hand-pinching to prevent rattling in the case of an undersized one.

The hexagonal configuration of the springy clip formed as straight-sided segments limits the engagement of the clip on the dimple to a few lines of contact only. In lamps where the outer envelope is internally coated with phosphor, this has the advantage of reducing to a minimum the amount of phosphor dislodged by the clip.

While the invention has been most useful to date in conjunction with high pressure mercury vapor lamps and has been so illustrated and described, it is equally applicable to other types of electric discharge devices involving a dual envelope construction such as high pressure sodium vapor. lamps wherein the are tubes are made of alumina ceramic.

What .I claim as new and desire to secure by Letters Patent of the United States is:

1. A jacketed electric discharge lamp comprising a vitreous outer envelope having a base at one end andan inwardlyturned dimple at the other, an inner'arc tube within said, outer envelope, atrame supporting said are tube within said outer, envelope and including a transverse portion at said other end, said transverse portion forming a half-loop around said dimple and clear of it, and a springy clip attached to said transverse portion and encircling said dimple except for a narrow gap, said clip a being so oriented that the gap faces the inside of said mediate point to said transverse portion.

4. A lamp as defined in claim 1 wherein said clip consists of a springy metal band having straight-sided segments and forming a loop with a narrow gap therein.

No references cited.

JAMEs w. LAWRENCE, Primary Examiner. R. F. HOSSFELD, Assistant Examiner. 

1. A JACKETED ELECTRIC DISCHARGE LAMP COMPRISING A VITREOUS OUTER ENVELOPE HAVING A BASE AT ONE END AND AN INWARDLY TURNED DIMPLE AT THE OTHER, AN INNER ARE TUBE WITHIN SAID OUTER ENVELOPE, A FRAME SUPPORTING SAID ARC TUBE WITHIN SAID OUTER ENVELOPE AND INCLUDING A TRANSVERSE PORTION AT SAID OTHER END, AND TRANSVERSE PORTION FORMING A HALF-LOOP AROUND SAID DIMPLE AND CLEAR OF IT, AND A SPRINGY CLIP ATTACHED TO SAID TRANSVERSE PORTION AND ENCIRCLING SAID DIMPLE EXCEPT FOR A NARROW GAP, SAID CLIP BEING SO ORIENTED THAT THE GAP FACES THE INSIDE OF SAID HALF-LOOP, SAID CLIP PROVIDING SUPPORT TO SAID FRAME AT SAID OTHER END. 